CPU+memory usage

[nancy0703]

I have a pentium 4 (3.6GHz) with HT and 3GB memory. I am currently running a number of simulations using an old DOS application. I mentioned that the CPU usage is only 50% and the memory usage is 256. Is HT responsible for this? Will it make any difference if I disable it from BIOS? What about the memory usage? Any improvement will make a big difference to me in terms of time...Thanks in advance

[Steven_L_Intel1]

It isn't really 50%. That's just the Windows task monitor being confused by HyperThreading. It doesn't know how to account for the second "virtual" CPU, which certainly doesn't perform as if it were an additional CPU or core.

I don't understand your comment about memory. What problem are you seeing?

[nancy0703]

Steve thank you for your reply.However do you think that for a dos application it will be better (in terms of analysis time) to disable the HT? For the memory usage I think it is to low,thus I do not take any advantage of the avaliable resources when running my simulations..:smileysad:

[Steven_L_Intel1]

It is not likely to make much difference. Your system is running some background tasks and those can take advantage of HT. Try it both ways and see what works best for you.

[nancy0703]

Thanks again Steve for your reply.However I am still confused.Running an old dos application to a new PC means that you can't get anyclose ingeting the best from the system's avaliable resources?It seems to methat I could have the same results (in terms of speed)using a much older PC having a 512 memory instead of 3GB. Also I tried to disable HT and now although the task manager shows 100% CPU usage,my system seems more unstable (I can not do anything else)and I am getting no noticeable difference in the analysis speed.

[Steven_L_Intel1]

I assume that by a "DOS application" you mean a console application. You need to determine what is limiting you. If you're seeing 100% CPU utilization, then it probably isn't memory or disk. Your application will use only so much memory - adding more RAM doesn't make a program run faster if it has all the RAM it needs.

I would not expect disabling HT to make a system unstable. It will be somewhat less responsive while running a CPU-bound program.

What switches are you using in DVF and in Intel Fortran to build?

[nancy0703]

There is no need to rebuild this program (writen in Fortran).....it's an old and trusted engineering executable program which I run several times for the needs of my simulations. I am just trying to find ways of improving its performance (i.e. using more of my system's resources). I guess that there are some ways to improve the performance of an old dos application running in windows.

[Intel_C_Intel]

Hello,

My experience is that an old Fortran code, compiled with DVF, almost always may be significantly faster if it is being recompiled, usingIVF,to target new hardware instructions. In this way you can use more of the hardware efficiently, as many applications spend quite some time to wait for instructions and data from the memory. The idea behind HT is that another application can use the hardware while your application is waiting for dataor instructions from memory. However, if your program is really well optimized, for example by using the latest IVF compiler with Profile Guided Optimization, you will notice that other applications may not be running so efficiently due to HT anymore, as your application do not spend so much time waiting for data and there is less room for other applications to run in the background.

Lars Petter Endresen

[nancy0703]

Lars thank you for your reply. I will try to recomplile this application (it will be a difficult task) as you suggested tocheck if it makes any difference. For the HT when disabled I notice that other applications were not run very efficiently compared towhen itwasenabled. HoweverI didn't notice any differencein terms of increasing my program's speed.Why that happens?Does it mean that my application uses more resources or that it uses the availiable resources in an inefficient way?At the end of the day I guess that I can not get closer to my PC's best performance and I have to compromise. Any other suggestions are more than welcome

[Intel_C_Intel]

Does it mean that my application uses more resources or that it uses the availiable resources in an inefficient way?

On most modern computers most programs spend quite some time to wait for data and instructions from the main memory, so if I would guess, yes I would think that also your application uses the availiable resources in an inefficient way. This is nothing unusual however - it can be quitedifficult to use all available resources all the time asthis requiresa perfectly balancedmixture of instructions (most modern computers aregood at running numerous programs simultaneously).

Tuning your application may be a lot easier using Intel VTune in addition to Intel Fortran. By the way, your choice of hardware Intel Pentium 4 3.6 GHz is indeedgreat - in particular if your application is floating point intensive.

Lars Petter Endresen

[nancy0703]

Thank you very much indeed Lars

[Intel_C_Intel]

I am currently running a number of simulations using an old DOS application.

If you canexecute two simulations simultaneously, then you will see that, due to HT, they will use less time than if they are executed after one another. Typically two simulations thattake 10 minutes each may take around 15 minutes if you run them simultaneously on a Pentium 4 with HT. Running them after one another will of course take 20 minutes, so you save about 5 minutes (you can take a 5 minute coffee break instead :-).

Lars Petter Endresen